LOCOMOTIVE ENGINE AND RAILWAY GRADIENTS. 161 



cumstances; the lighter trains with a single engine, and 

 the heavier ones with a double or assistant engine. In the 

 latter case, it is curious to observe the comparatively small 

 power which in many instances was given out by the 

 assistant engine, and the increased quantity of work per- 

 formed by the single one. In Table I. the single engine 

 ascends the gradients, on an average duty of three months 

 of 38 ascents, with 71*6 tonSj at the rate of 6 '31 miles an 

 hour ; whereas the average duty of the two engines — 

 Table II. — in 10 ascents with 11 1*9 tons, was at precisely 

 the same speed, or 6'31 miles an hour. 



Again, in 15 ascents of the double engines conveying a 

 load of 123*9 tons, the speed was only 5*9 miles per hour, 

 showing an evident saving in the use of the single engine 

 and light trains to a very considerable amount. The re- 

 sults of the experiments are therefore in favour of one 

 engine, which carried 71*6 tons up the incline at the rate of 

 6*31 miles an hour, whilst the assistant engine carried only 

 40*3 tons at the same rate. This gives an excess of duty of 

 31 '3 tons in favour of working the gradients by the single 

 engine. In this comparison we must, however, assume 

 the leading engine of the heavy trains to be equally power- 

 ful with that of the lighter one. The following tables are 

 however more explicit,- and exhibit some curious and im- 

 portant facts in the working of railway gradients. 



